How to control yellowing of plastic products? ?

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Reasons for the yellowing of plastic products and solutions; the yellowing of plastic products is caused by the aging or degradation of the material, and it is a common form of aging phenomenon. Improper quality of raw materials, formulation, manufacturing processes, and storage methods can all lead to the yellowing of plastics. Generally, the yellowing of plastic products is caused by the aging or degradation of the material; in the case of PP, this yellowing results from aging (degradation). Due to the presence of side groups on polypropylene, its stability is poor, especially when exposed to light. Generally, a light stabilizer is added. As for PE, due to the absence of side groups, yellowing during processing or in the early stages of use is not common. PVC does tend to yellow, which is largely related to the product’s formulation; HCL may be produced as a result. In simple terms, it’s oxidation; the surface of some masterbatches tends to oxidize easily, so it is necessary to treat their surfaces. Adding high-molecular lubricants to plastic extruders serves to form a flowable high-molecular fluoropolymer film on the machine walls, thereby improving the extrusion properties of polyolefin resins, as well as the extrusion pressure and processing temperature. This approach enhances product quality and production capacity, reduces production costs, minimizes or eliminates melt fracture, and lowers the defect rate. If yellowing due to plastic remains even after addition, it may be due to issues with the quality of the ultraviolet absorber, an incorrect formula, or an insufficient amount of it used. Yellowing will not occur after using the correct UV absorbers, as the purpose of these additives is to prevent plastics from yellowing. When adding ultraviolet absorbers, does the color of the absorbers themselves affect the color variation in the plastic products? If that is the case, it does have an impact, and it is necessary to choose ultraviolet absorbers of other colors. So, how can plastic yellowing be controlled? 1. Origin of the problem: Over time, both the inner and outer surfaces of the shell gradually turn yellow, and this persists even after cleaning. Reason: Ultraviolet radiation and heat cause the degradation and aging of plastics. 2. Solutions: (1) From a material perspective, a) bromine-based flame retardants can cause yellowing, and they are also not permitted under RoHS regulations. b. Due to the intense shearing forces during the processing of modified plastic formulations, antioxidants must be added to prevent thermal decomposition, which could cause the raw materials to turn yellow ； The body material does not yellow easily. For example, Chemtura Ultranox 641 is the best secondary antioxidant, costing over 200 RMB/kg; phosphites such as 626, as well as liquid phosphites like Weston and solid phosphites like Ultranox, also offer good performance. c. Special UV-resistant powder, along with special light stabilizers and antioxidants 1010 and 168, each added in an amount of around 0.5%. d. Some blue pigment can also be added, because blue + yellow equals white. e. Titanium dioxide fillers can also cause yellowing; note that it is not the titanium in them that is to blame, but rather the limestone powder contained within. (2) Spray a dark color on the surface. (3) Apply an anti-UV coating to the surface. (4) Treatment of yellowed plastic surfaces: Clean with 10-15% hydrogen peroxide (H2O2), and then apply an anti-UV coating. (5) Prevention: Avoid exposure to sunlight and heat sources.